Typical transonic fans for turbofan engines have a rather high relative tip Mach number, for example approximately 1.5. This usually leads to shock losses and boundary layer separation, which reduce fan tip efficiency, and accordingly reduce the overall efficiency of the fan.
Moreover, the tip section of the fan blade leading edge, being the least structurally supported area of the blade, is generally most at risk of damage, for example due to foreign object damage (FOD).